In electrophotography, an imaging system forms a latent image by exposing select portions of an electrostatically charged photoconductive surface to laser light. Essentially, the density of the electrostatic charge on the photoconductive surface is altered in areas exposed to a laser beam relative to those areas unexposed to the laser beam. The latent electrostatic image thus created is developed into a visible image by exposing the photoconductive surface to toner, which contains pigment components and thermoplastic components. When so exposed, the toner is attracted to the photoconductive surface in a manner that corresponds to the electrostatic density altered by the laser beam. The toner pattern is subsequently transferred from the photoconductive surface to the surface of a print substrate, such as paper, which has been given an electrostatic charge opposite that of the toner. The substrate then passes through a fuser assembly that applies heat and pressure thereto. The applied heat causes constituents including the thermoplastic components of the toner to flow onto the surface and into the interstices between the fibers of the substrate. The applied pressure produces intimate contact between toner and fibers and promotes settling of the toner constituents into these interstitial spaces. As the toner subsequently cools, it solidifies adhering the image to the substrate.
The fuser assembly typically includes cooperating fusing members that form a nip area capable of delivering heat and pressure to the substrate passing through the nip. Exemplary nip forming members include a fuser roll and a backup roll, a fuser roll and a backup belt and a fuser belt and backup roll. A heat source associated with one or both of the nip forming members raises the temperature of the fusing members at the nip area to a temperature required by a particular fusing application. As the substrate passes through the nip area, the toner is adhered to the substrate by the pressure between the nip forming members at the nip area and the heat resident in the fusing region.